11/13/13 Atmos. Chem. Lecture 17, 11/13/13: Partculate mater: Size and behavior Intro to partculate mater Size distributons Partcle moton: Difusion, setling PSet 4 due Monday Nov. 25
Monday's reading: add in 461-464
Atmospheric partculate mater ("aerosol")
Aerosol: a (relatvely stable) suspension of solid or liquid partcles in a gas
Aerosol partcles: the condensed-phase part of the aerosol
Generally: atmospheric aerosol involves partcles of diameter 1 nm-100 μm
MODIS image from NASA (courtesy of Jacques Descloitres,
MODIS Land Rapid Response Team, NASA/GSFC)
Moderate Resoluton Imaging Spectroradiometer (MODIS):
htp://www.nasa.gov/vision/earth/environment/partculate polluton.html
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11/13/13 Types, sizes of aerosol partcles
This image is in public domain.
Oberd6rster, Oberd6rster, and Oberd6rster,
Env. Health Perspectves 113:823 (200S)
Partcle size measurements: discrete bins
Images removed due to copyright restrictions. See Table 8.1 in Seinfeld, J. H.,
and S. H. Pandis. Atmospheric Chemistry and Physics 2nd ed. Wiley 2006.
S&P 2
11/13/13 Partcle size measurements: discrete bins
Images removed due to copyright restrictions. See Table 8.1 in Seinfeld, J. H.,
and S. H. Pandis. Atmospheric Chemistry and Physics 2nd ed. Wiley 2006.
S&P Number, surface area, and volume distributons
Image removed due to copyright restrictions. See Figure 8.1 in Seinfeld, J. H.,
and S. H. Pandis. Atmospheric Chemistry and Physics, 2nd ed. Wiley 2006.
S&P 3
11/13/13 Dynamic range: Log Dp space
Image removed due to copyright restrictions. See Figure 8.5 in Seinfeld, J. H.,
andS. H. Pandis. Atmospheric Chemistry and Physics, 2nd ed. Wiley 2006.
S&P Dynamic range: Ln Dp space
Image removed due to copyright restrictions. See Figure 8.6 in Seinfeld, J. H.,
and S. H. Pandis. Atmospheric Chemistry and Physics, 2nd ed. Wiley 2006.
S&P 4
11/13/13 Number, surface area, volume distributons: Urban area
Image removed due to copyright restrictions. See Figure 8.11 in Seinfeld, J. H.,
and S. H. Pandis. Atmospheric Chemistry and Physics, 2nd ed. Wiley 2006.
S&P Moton of a partcle in air
partcle of
diameter
p
We want to consider:
1)  drag force by the air
2)  efect of an external force (e.g., gravity)
gas
molecules
3)  Brownian difusion
velocity
v
[Note: Additional material is discussed here during lecture.]
S
11/13/13 Diferent regimes of the partcle in air Image removed due to copyright restrictions. See Fig. 9.1 in Seinfeld, J. H.,
and S. H. Pandis. Atmospheric Chemistry and Physics 2nd ed. Wiley 2006.
S&P Fig 9.1 Slip correcton factor Cc
Image removed due to copyright restrictions. See Fig. 9.3 in Seinfeld, J. H.,
and S. H. Pandis. Atmospheric Chemistry and Physics 2nd ed. Wiley 2006.
S&P 6
11/13/13 �fect of gravity, difusion
Image removed due to copyright restrictions. See Figures 9.6 and 9.8 in Seinfeld,
J. H., and S. H. Pandis. Atmospheric Chemistry and Physics, 2nd ed. Wiley 2006.
S&P Implicatons for human health
Oberd6rster, Oberd6rster, and Oberd6rster,
Env. Health Perspectves 113:823 (200S)
This image is in public domain.
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11/13/13 What is a "diameter"?
Not all partcles are spherical! Physical diameter becomes meaningless. Measurement techniques ofen get size informaton from mobility, terminal velocity, etc. →  Need to use equivalent diameters
Volume equivalent diameter Dve: diameter of sphere of same volume as the partcle of
interest
Aerodynamic diameter Da: diameter of a sphere of unit density (1 g/cm3) that has the
same terminal velocity of the partcle of interest
Vacuum aerodynamic diameter Dva: diameter of a sphere of unit density (1 g/cm3) that
in the free molecular regime has the same terminal velocity of the partcle of interest
Electrical mobility diameter Dm: diameter of a charged sphere that has the same
migraton velocity in a fxed electric feld as the charged partcle of interest
see DeCarlo et al., Aerosol Sci. Technol., 38:118S (2004)
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